1. Field of Invention
The present invention relates to an improved driving apparatus that permits bicycles and the like to be more efficiently powered by movement of a user's legs in an up and down motion. Furthermore, the improved bicycle driving apparatus of the present invention includes a variable transmission assembly permitting a user to choose among an almost unlimited number of gear or speed settings and to smoothly and uniformly shift between these gear or speed settings.
2. Description of the Related Art
The bicycle has been steadily increasing in popularity as a means of transportation, recreation, and fitness. The development of new lightweight metal alloys and other materials have increased the efficiency of bicycles while providing sturdy and durable bicycle designs. Other improvements, such as those permitting a user to shift gears or speeds, have also increased the efficiency and user's enjoyment of bicycles successfully. However, few improvements have increased the efficiency of bicycles by focusing upon the particular leg movements utilized in pedaling so as to impart movement to the bicycle.
Generally, in order to impart movement to a bicycle, a bicyclist moves his legs in a circular manner, and thus, the pedals of the bicycle move in a circular manner, as well and translate into causing the wheels of the bicycle to move forward. Specifically, a user's legs must continuously move the pedals through a forward circular motion of 360 degrees. This type of pedaling motion provides a simplistic design which is relatively easy and inexpensive to manufacture, and which has for the most part, gained universal acceptance, despite the inefficiency inherent in transmitting force by leg movements through a 360 degree circular movement as shown in FIG. 1b. In particular, when a bicyclist's legs move through a 360 degree circular pedaling movement, the majority of force is applied during the downward portion of the forward stroke, "A", as indicated by the arrow marked "A" in FIG. 1b. During this downward portion of the forward stroke, a bicyclist utilizes his or her own body weight advantageously to apply substantial vertical forces and cause forward movement of the bicycle. On the other hand, the top and bottom portions of a circular pedalling stroke require the application of almost entirely horizontal forces. These portions of the pedaling movement are indicated by the arrows marked "B" in FIG. 1b. Naturally, a bicyclist sitting on a bicycle cannot adequately apply horizontal forces to a pedaling mechanism located directly below him or her, as they are very difficult to apply. As such, a significant portion of the 360 degree circular pedal movement is ineffectual in transmitting force or movement to the rear wheel of the bicycle.
Others in the art have struggled to develop a bicycle driving apparatus structured to reduce this inefficiency inherent in a circular pedaling motion of 360 degrees. For example, some prior devices have attempted to limit the motion of the pedals to less than 360 degrees in order to eliminate the "inefficient zones" at the top and bottom of 360 degree pedal movement, such as are labelled B" in FIG. 1b. Existing devices have generally proven to be inadequate, however, in that they entail a variety of intricate parts and a complicated assembly, and in general, they fail to provide a practical solution to eliminating the "inefficient zones" of circular pedal movement.
Furthermore, existing devices have been inadequate in providing a speed-shifting mechanism structured for use with a bicycle driving apparatus which limits the pedal motion to less than 360 degrees. Indeed, the need for a variable speed transmission increases with bicycle or similar device which has a limited range of pedal movement, due to the fatigue that results from the alternating direction of a restricted pedalling movement. Additionally, the ability to vary the amount of force required for pedal movement becomes even more critical when the user must travel uphill, against the wind, or in rough terrain. In conventional bicycle designs which include a variable speed transmission, a complicated series of different sized sprockets are typically disposed on the rear wheel, such that each sprocket size corresponds to a desired "speed" or "gear" for the bicycle. These known designs also typically include a complicated assembly for moving the drive chain from one sprocket to another so as to adjust the speed. Such a speed shifting assembly usually includes several intricate and delicate parts, thereby making the assembly difficult to maintain and readily susceptible to mechanical failures. Furthermore, a user is naturally limited in his or her choice of gears or speeds utilized in existing variable speed transmissions, since a different sprocket must be provided for each speed selected. Moreover, due to the different sized sprockets, a shift in gears typically causes an abrupt change in the pedalling force required and often results in an unsteady and jarring transition between speeds. These problems are further intensified when the circular motion of the pedals is limited to less than 360 degrees, as it will be understood that such a limitation requires the pedals to move in an alternating "up and down" direction, as opposed to a continuous, smooth circular, motion. The lack of a smoothly variable transmission having an infinite number of speed settings further adds to the impracticality of existing devices, since a bicyclist is not able to overcome his or her fatigue by shifting to an easier gear in a smooth and uniform manner. Due to the inability of others in the art to provide a practical and convenient bicycle driving apparatus which limits the circular pedaling motion to less than 360 degrees, it is not surprising that the conventional 360 circular motion apparatus has continued to enjoy universal acceptance in spite of its highly inefficient pedaling mechanism.
Accordingly, there still remains a significant need in the art for a bicycle driving apparatus which limits pedaling motion to the downward portion of the forward stroke in order to eliminate pedal movement through the "inefficient zones" at the top and bottom of a conventional circular 360 degree pedal movement. In particular, there is a need for such a bicycle driving apparatus which is simplistic in design, convenient, and practical. Additionally, in order to overcome problems inherent in prior limited pedal motion devices, there is a need for such a device which includes a smooth shifting transmission so as to permit a cyclist to smoothly and uniformly shift between an infinite variety of speeds or gears to adapt to varying conditions.